As wireless transmission technologies are well developed, wireless data receiving and transmission become basic functions of many electronic apparatuses. For example, a notebook computer can support the functions of transmitting many different wireless network signals including wireless local area network (WLAN) signals, wireless Bluetooth signals and digital television signals, etc. To receive these wireless signals at different bands, it is necessary to build many antennas in the notebook computer. Referring to FIG. 1 for the design of a traditional antenna of a notebook computer 1, the notebook computer 1 installs two detachable antennas 13, 14 around a screen 12 in a casing 11, and the size of the antennas 13, 14 is restricted by the limited available space around the periphery of the screen 12.
As to the radio frequency signals with a frequency of 2.4 GHz or 5 GHz, only a small antenna is sufficient. For example, the length of a dipole antenna with a primary frequency of 5 GHz is approximately equal to 3 cm, and the antenna with a primary frequency of 2.4 GHz is approximately equal to 6 cm. For signals with a lower frequency such as the very high frequency (VHF) signal (45 MHz˜300 MHz) or the ultra high frequency (UHF) signal (300 MHz˜900 MHz) of a digital television, the required length of the antenna is very long. For instance, the length of a dipole antenna with a primary frequency of 150 MHz is approximately equal to 100 cm, and the length of a planar inverted F antenna (PIFA) with a primary frequency of 150 MHz is approximately equal to 70 cm. As mentioned in these situations, it is quite difficult to install such a long detectable antenna into a notebook computer 1 in accordance with the prior art, and thus the notebook computer 1 requires a connecting device such as a SMB or MMCX connector to connect an external antenna 15 for receiving or transmitting a signal of a lower frequency. However, the use of an external antenna 15 not only bends or breaks the antenna easily due to collisions, but also causes inconvenience for users to carry and use the antenna.
As wireless communication applications become popular, various different portable electronic apparatuses are equipped with a wireless communication module. If the antenna is installed near a display device, the clock multiplication of the display device will interfere with signals within the operating band of the antenna, and thus lowering the wireless communication performance. For instance, a notebook computer comes with a GSM communication module, and its operating band falls in the range from 880 MHz to 915 Hz, and its antenna is installed in a display device casing of the notebook computer, and the clock of 70 MHz is adopted by the display device of the notebook computer for updating images, then the multiplication of the clock signal by 13 times (910 MHz) will interfere signals within the GSM operating band. If the electronic apparatus is equipped with only one kind of wireless communication module, then the aforementioned interference can be avoided by using a hardware circuit design. However, there are more and more wireless communication modules installed in an electronic apparatus, and one set of notebook computer may have a GSM communication module, a WCDMA communication module and a WLAN communication module at the same time. The band used for one kind of wireless communication module is different from the other, and the chance of having an interfered band is increased drastically, and the traditional hardware circuit design is no longer sufficient for preventing interferences.
In view of the shortcomings of the prior art, the inventor of the present invention based on years of experience in the antenna field to conduct experiments and modifications, and finally developed an electronic apparatus with an antenna, its anti-jamming system and its method to overcome the foregoing shortcomings.